Electrical circuits



March 5, 1929.

L. W. AUSTIN ELECTRICAL CIRCUITS Filed Jan. 25, 1924 gnvewfo'l,

Louis 14: Austin Patented Mar. 5, 1929.

l'lED STATES PATE T OFFICE,

LOUIS w. AUSTIN, or WASHINGTON, DISTRICT or COLUMBIA.

ELECTRICAL CIRCUITS.

Apphcation filed awa 1924. Serial ,No. scans.

My invention. relates generally to electrical circuits, and particularly those in Whichhigh frequency electrical currents are produced of the order of frequency connnonly used in radio communication, the particular object of my invention being to produce hi gh frequency electrical currents and maintain the frequencyconstant.

My invention is of particular value in receiving high frequency electrical currents by the heterodyne or beats methods, and is most effective in receiving such signals in the high or range of frequencies, for instance, 1000 kilo-cyc1es (300 meter Wave length).

It is Well known that in the use of a threeelectrode vacuum tube oscillator having coupled grid and plate circuits to produce oscillations, the period of the oscillation being set by the period of one or the other of these circuits, that variationsin the filament. temperature or variations in the plate circuit energy supply potential will cause variations in the frequency of the oscillationa'and these variations become particularly noticeable in,

receiving by heterodyne at the higher frequency Where a slight change in the frequency of a locally generated oscillation produces a substantial change In the frequency of the beat oscillations, or may even cause thebeat I oscillations to vary beyond the range of audibility.

It the principal purpose of my invention to prevent variations Within the vacuum tube from materially influencing the constants of the circuit determining the cillations of the system. v I V My invention will be best understood by reference to the accompanying drawing in which A represents a conventionaltype of antenna connected through inductance L; to a secondary oscillatory circuit L L G which circuit is connected to the grid G and filament F of the threeeelectrode vacuum tube period of the es VT throu 'h the Well known 'rid leak-sto a b I ping condenser combinatlon C, and R. The

flate circuit of the vacuum tube includes in ductance L telephones T and battery 15,, the telephones being shunted by the ordinary F radio frequency by-pass condenser 0,. III-- circuit including inductance L inductance L, and capacity C thiscircuit bemg preferably' one having a decrement lower than the decrement of-thecircuitL L (1,, and

the'coupling between'this intermediate circuit and the grid and plate circuits being preferably quite loose. t

I found that With the arrangement above described the frequency of the oscillations is set or fixed by the intermediate circuit, and

that variations in the vacuum tube Which may materially influence the period of the grid circuit do not manifest. themselves in the sys tem as a Whole, and that practical constancy of frequency may be obtained even at frequencies of the order of 1000 kilo-cycles per second. Any desired frequency may-be ol tained by controlling the constants of the intermediate circuit. It is also desirable in radio receiving to control the constants of the antennaand secondary circuits for more efli} cient reception through resonance, A more ready control may be obtained by mounting the condenser G and C, on a single shaft providing the inductances of the tWo circuits of WlllCll these condensers form apart are suitably designed to of this kind. i

l/Vhile I have described my invention in permit of an arrangement connection with the reception of radio si -L nals, ts application is not so hunted as there are many uses for a constant frequencyhigh frequency generator,

liaving described my invention I claim:

In a regenerative detector circuit having grid-lilament and plate-filament circuits, the combination of an antenna coil, a resonant circuit coupled thereto and located'in the grid-filament circuit of the vacuum tube,said

resonant circuit consisting of a plurality of 1 inductances and a condenser in parallel therewith, an inductance in the plate-filament circuit, and a lowdecrement clrcult loosely cou: pled toone of the inductances 1n the gridfilament circuit and tothe said inductance in circuit consisting of a plurality of inductances and a variable condenser, the inducthe plate-filament circuit, said low decrement ta'nces and condenser connected in series rela- I,

tion.

LoUIs W. AUsTIn 

